Optical coherence tomography (OCT) is a technique for obtaining high resolution cross-sectional images of tissues or materials, and enables real time visualization. The aim of the OCT techniques is to measure the time delay of light by using interferometry, such as via Fourier Transform or Michelson interferometers. A light from a light source delivers and splits into a reference arm and a sample (or measurement) arm with a splitter. A reference beam is reflected from a reference mirror (or other reflecting element) in the reference arm while a sample beam is reflected or scattered from a sample in the sample arm. Both beams combine (or are recombined) at the splitter and generate interference patterns. The output of the interferometer is detected with one or more detectors such as photodiodes or multi-array cameras, such as, but not limited to, in a spectrometer (e.g., a Fourier Transform infrared spectrometer). The interference patterns are generated only when the path length of the sample arm matches that of the reference arm to within the coherence length of the light source. By evaluating the output beam, a spectrum of an input radiation may be derived as a function of frequency.
The frequency of the interference patterns corresponds to the distance between the sample arm and the reference arm. The higher frequencies are, the more the path length differences are. The Fourier transforms are performed in order to obtain frequency distributions of the interference patterns to obtain axial back-scattering images. The reconstructed images are symmetric with respect to the zero delay of the interferometer, in other words, the longer arm and/or the shorter arm of both of the arms cannot be distinguished because of a real function of the detected interferometer patterns. To avoid complex mirror artifacts due to this ambiguity between the longer arm and the shorter arm, the zero delay is positioned outside of the images. Then, only half of imaging depth is available. In general, the sensitivity is highest around a zero delay position so that a signal to noise ratio (SNR) would be worse if the zero delay is positioned outside of the images.
However, previous attempts to overcome such complex mirror artifacts have not taken care of continuity of A-lines between frames. Because modulators are driven by saw-tooth waveform, response time is needed while operating from peak to bottom. Therefore, discontinuity from frame to frame happens, as shown in FIG. 1.
Accordingly, it would be desirable to provide at least one OCT technique for use in at least one optical device, assembly or system to achieve constant, stable A-lines over a sufficient predetermined period of time at high efficiency and a reasonable cost of manufacture and maintenance.